The Prostate, Lung, Colon-rectum and Ovary Cancer Screening Trial (PLCO) is designed to determine in screenees aged 60-74 years at entry whether: a. In females and males (1) screening with flexible sigmoidoscopy (60 cm sigmoidoscope) can reduce mortality from colo-rectal cancer; and, (2) screening with chest x-ray can reduce mortality from lung cancer. b. In males (1) screening with digital rectal examination plus serum prostate-specific antigen (PSA) can reduce mortality from prostate cancer; C. In females (1) screening with pelvic examination plus CA 125 and transvaginal ultrasound can reduce mortality from ovarian cancer; The Contractor shall establish a Study Coordinating and Data Management Center (CC) for the PLCO Cancer Screening Trial to develop and maintain systems and procedures needed for biomedical data management, study coordination, statistical analysis, and report writing. The CC in its coordination efforts acts as a liaison between the Screening Centers, the Central Blood Testing Facility (LAB), study consultants, and the National Cancer Institute Project Officers.